L-Allylglycine is an amino acid derivative that reduces glutamate decarboxylase (GAD) activity by 60% when administered at a dose of 39.8 μmol/g per hour ex vivo in mouse brain preparations. L-Allylglycine (1.2 mmol/kg, i.p.) induces convulsions and decreases GABA concentration throughout the cerebellum, pons, medulla, striatum, cortex, and hippocampus in mice. Chronic administration (3.2 μg/0.5 μl per hour for 13 days) of L-allylglycine in rats increases locomotor activity in an open field test and impairs attention in the 5-choice serial reaction time task (5CSRTT). In vitro, L-allylglycine inhibits GAD only when used at high concentrations (1-80 mM). The more potent in vivo activity can be attributed to metabolic conversion of L-allylglycine to 2-keto-4-pentanoic acid, a more potent convulsant and GAD inhibitor.